1. Field of the Invention
The present invention is directed to an image display generator or projector for a head-up display, and more particularly to an image display generator comprised of a plurality of light emitting diodes (LEDs) which are individually selectively activatable to emit light for collectively defining or forming an image.
2. Description of the Related Art
In current implementations of head-up displays, such as those used in advanced aircraft, an image projectorxe2x80x94which may, for example, comprise a cathode ray tube to which the image to be projected is electronically fedxe2x80x94outputs a visually-perceptible image. The image output from the projector is then directed through a diffractive optics lens to collimate the image, after which the collimated image is reflected, by one or a series of full or partial reflectors, into the pilot""s view or sight path for viewing of the projected image in overlaid concurrency with objects located outside of the cockpit windshield or window. The electrical, mechanical and optical components that form such a head-up display understandably require a not insignificant volume of space in the aircraft, and more particularly in and adjacent the cockpit and instrumentation baysxe2x80x94space which is at a tremendous premium in any aircraft. Such CRTs also generate undue amounts of heat that must be dissipated from the source. Although the use of a flat panel liquid crystal display (LCD) as an image projector, in lieu of a cathode ray tube, will somewhat reduce the space required to implement the head-up display apparatus, it remains necessary to direct the image from the LCD through collimating optics located in the light path from the projector prior to its reflection into the sight path of the pilot or flight crew, thus preventing truly significant reduction in the amount of space required for such apparatus. Collimation of the image is required so that the projected image from the head-up display and manipulated into the sight path of the pilot will appear to the pilot to be focussed at infinity, thus permitting the pilot to concurrently see the projected image and objects outside of the aircraft without having to refocus his or her eyes to view one or the other.
The present invention is directed to an image display generator which solves the aforementioned problems of the prior art by, inter alia, shrinking the image projector to a unitary construction of the thickness of a relatively thick semiconductor wafer, whereby the wafer directly outputs and projects a collimated image that can accordingly be directly reflected into the sight path of the pilot. As a consequence, the inventive display generator or projectorxe2x80x94which may, by way of example, in practice have a thickness of about or less than one-quarter inch (xc2xcxe2x80x3)xe2x80x94can be mounted closely proximate or adjacent a partially-reflective reflector with which the projected image from the wafer is redirected into the sight path of the pilot.
In accordance with the invention, a unitary display structure is created which incorporates the illuminatable LEDs and a corresponding plurality of lenses for capturing and collimating the light emitted by the actuated LEDs. This is accomplished by providing a sheet of transparent substrate material (such as Sapphire) of substantially uniform thickness and forming or depositing a layer of semiconductor material on one surface of the sheet. LED junctions are formed in the semiconductor layer, and a layer of insulating material is then disposed over the LED-containing semiconductor layer and coated with a layer of reflective material. The opposite or exposed substrate sheet surface is etched or machined or otherwise configured to form in the surface lenses aligned with the LEDs for receiving and collimating light emitted by the LEDs for use in a display.
In a preferred embodiment, the reflective layer regions located proximate the LEDs are contoured to direct light from the LEDs by reflection from the reflective surface, to the lenses, wherein each respective lens, LED and contoured reflective region are in alignment with each other.
In another preferred embodiment, openings are formed in the reflective layer to allow a small portion of the generated light from the LED to be received through the openings by a respective one of a plurality of optical detectors for monitoring the performance of the LEDs.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate and disclose the structures and procedures described herein.